The present invention relates to the electrical and mechanical mounting of electrical headers and connectors to printed circuit boards in such a way that electric field propagation from the individual signal carrying conductors is minimized.
Electrical connectors and headers are used to effect electrical connection to and from printed circuit boards and typically include a housing and an array of receptacles or pins supported in the housing for mating connection with a similar array of pins or receptacles of the corresponding header or connector. Each pin or receptacle includes a "tail" portion that extends from the housing to define an array of tail portions that are designed to be received within and passed through an array of holes on the printed circuit board. The tail portions can extend rearwardly in a straight-line fashion from the housing or can be bent at a right angle relative to the principal mating axis of the contact pair.
In many electronic systems, it is important that the various interconnected circuits be shielded or otherwise protected from external electric fields and, conversely, that any electric fields developed from those circuits be prevented from propagating to other circuits. The problem is of particular concern in signal-bus applications in which higher bus speeds and the attendant signal transitions cause electromagnetic interference that can adversely affect adjacent circuits. Headers that use straight-back tail portions are typically mounted upon the printed circuit board so that the tail portion length, and its attendant antenna effect, is minimal. The situation is somewhat different with regard to right-angle mounting arrangements since the tail portions extend rearwardly from the housing and then extend at a right angle to provide a substantially longer tail portion in which the segment lengths can provide a measure of wavelength-matching at certain signal speeds.
While the straight-back approach provides a minimum tail length and minimal consequent antenna effect, the design is not well suited for use in card-cage type packaging systems which printed circuit boards are mounted in closely adjacent positions. In traditional circuit board designs, electromagnetic interference can be addressed by providing a full-shield housing or other shield structure to prevent electric field emission and provide a measure of protection against external radiation. While shielding can prevent radiation from emanating from a signal carrying set of circuit conductors, it oftentimes represents an extra cost increment not consistent with cost-effective connector systems. In addition, shielding oftentimes does not address the problem of inter-circuit interference between or among the various tail portions. Accordingly, a need arises for a cost-effective technique which prevents or at least attenuates radiation from signal carrying circuits and prevents those circuits from being adversely affected by external fields.